1. Field of the Invention
This invention is generally directed to drilling rigs used for creating wells or blast holes and more particularly to a top head drive and mast assembly which is adapted to be mounted to a conventional mast or derrick of a drill rig such that the drill rig can operate with a rotary top head drive. In a preferred embodiment, the invention will be described as being mounted to a conventional cable drilling rig wherein the top head rotary drive may be easily moved into position for rotary drilling and stabilized in position for advancing a drill string. The top head rotary drive and mast assembly can easily be raised and moved into close proximity with an existing mast or derrick, such as a derrick of cable drill rig, such that the top head rotary drive and mast are out of alignment with a drill hole thus allowing conventional drilling equipment to be fully operational.
2. Brief Discussion of the Related Art
In the boring or drilling of wells or blast holes and the placing of well casing or lining, generally two types of drilling rigs are used. A first rig, known as a cable drill rig, operates using a bit and drill stem which is raised and lowered for impact by a cable system.
As opposed to the reciprocal driving movement created by a cable rig, other rigs, known as rotary air rigs, provide rotation and compressed air through a drill string for drilling. Generally, such rotary air rigs are more efficient in generating greater drilling speeds for drilling wells in a more expeditious manner.
Conventional rotary air rigs incorporate a drill table mounted along a base of a mast. The rotary table includes a drive motor. In order to drill utilizing a rotary table, a kelly system is required wherein a kelly rod is connected to each section of drill pipe as the drill string is lowered. Because of the requirement for the drive kelly to engage within a chuck of the rotary drive head, a significant amount of time and labor is required when adding or removing a pipe section to a drill string as the kelly must be removed from the uppermost drill pipe section during each step.
To overcome the deficiencies of rotary table drive systems, newer top head rotary drive systems have been developed. Top head drive systems include a rotary drive head driven by one or more motors. The rotary drive heads are guided in a vertically reciprocating motion along rails of masts of such systems. Various types of assemblies may be utilized to raise and lower the top head rotary units during use. The benefit of the direct or top head rotary drive system is that the kelly bar required for drive tables is not necessary and the top head rotary drives may be connected directly, or through a coupling member, to an uppermost pipe section of a drill string.
It is preferred that the top head air rotary drive be used when retrieving and or replacing sections of a drill string for purposes of replacing a drill bit, such as in a sequence of tripping out sections of a drill string to replace a drill bit and tripping in pipe sections to reform the drill string.
In view of the foregoing, there remains a need to adapt vehicles having derricks, including conventional cable drilling rigs, such that they may operate with top head rotary drives which may be easily moved into a drilling position to facilitate the expeditious drilling of a bore or well hole and yet can be easily moved out of alignment position with the hole to permit the use of other equipment such as conventional cable equipment.
Some examples of prior art top head rotary drive drill systems are disclosed in the U.S. Pat. No. 3,994,350 to Smith et al., U.S. Pat. No. 4,421,179 to Boyadjieff, U.S. Pat. No. 4,589,503 to Johnson et al., U.S. Pat. No. 4,800,968 to Shaw et al., U.S. Pat. No. 5,038,871 to Dinsdale, U.S. Pat. No. 5,107,941 to Berry, U.S. Pat. No. 5,501,286 to Berry, and U.S. Pat. No. 5,794,723 to Caneer, Jr. et al.